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Publication numberUS4721779 A
Publication typeGrant
Application numberUS 06/893,268
Publication dateJan 26, 1988
Filing dateAug 5, 1986
Priority dateAug 22, 1985
Fee statusLapsed
Also published asDE3529988A1
Publication number06893268, 893268, US 4721779 A, US 4721779A, US-A-4721779, US4721779 A, US4721779A
InventorsKarl-Heinz Etzbach
Original AssigneeBasf Aktiengesellschaft
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Electrooptical apparatus
US 4721779 A
Abstract
Trisazo compounds of the formula ##STR1## where Z is ##STR2## X and Y independently of one another are each C1 -C24 -alkoxy, benzyloxy, phenylethoxy, mono-C1 -C24 -alkylamino, monobenzylamino, monophenylethylamino, monophenylamino, bis-C1 -C24 -alkylamino, N-C1 -C12 -alkyl-N-benzylamino, N-C1 -C12 -alkyl-N-phenylethylamino or N-C1 -C12 -alkyl-N-phenylamino, where the benzene rings are unsubstituted or substituted by C1 -C12 -alkyl, cyclohexyl, 4-C1 -C12 -alkylcyclohexyl, C1 -C24 -alkoxy, phenoxy or C1 -C24 -alkanoyloxy, R1, R2, R3, R4, R5 and R6 independently of one another are each hydrogen, methyl, methoxy, or chlorine and R7 is hydrogen or methyl, and the ring A or B may furthermore carry a fused benzene ring, are very useful as dyes in liquid crystal media, for example for electrooptical displays.
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Claims(8)
I claim:
1. An asymmetric trisazo compound of the formula ##STR26## where Z is ##STR27## X and Y independently of one another are each C1 -C24 -alkoxy, benzyloxy, phenylethoxy, mono-C1 -C24 -alkylamino, monobenzylamino, monophenylethylamino, monophenylamino, bis-C1 -C24 -alkylamino, N-C1 -C12 -alkyl-N-benzylamino, N-C1 -C12 -alkyl-N-phenylethylamino or N-C1 -C12 -alkyl-N-phenylamino, where the benzene rings are unsubstituted or substituted by C1 -C12 -alkyl, cyclohexyl, 4-C1 -C12 -alkylcyclohexyl, C1 -C24 -alkoxy, phenoxy or C1 -C24 -alkanoyloxy, R1, R2, R3, R4, R5 and R6 independently of one another are each hydrogen, methyl, methoxy or chlorine and R7 is hydrogen or methyl, and each of the rings A or B is a single ring or has fused thereto a benzene ring.
2. A trisazo compound as claimed in claim 1, wherein Z is ##STR28##
3. A trisazo compound as claimed in claim 1, wherein R1, R2, R3 and R4 are each hydrogen.
4. A trisazo compound as claimed in claim 1, wherein R5 is hydrogen and R6 .sbsp.methyl.
5. A trisazo compound as claimed in claim 1, wherein Y is mono-C1 -C24 -alkylamino, monobenzylamino, monophenylethylamino, monophenylamino, bis-C1 -C24 -alkylamino, N-C1 -C12 -alkyl-N-benzylamino, N-C1 -C12 -alkyl-N-phenylethylamino or N-C1 -C12 -alkyl-N-phenylamino and X is C1 -C24 -alkoxy, benzyloxy or phenylethoxy, where in each case the benzene rings are unsubstituted or substituted by C1 -C12 -alkyl, cyclohexyl, 4-C1 -C12 -alkylcyclohexyl, C1 -C24 -alkoxy, phenoxy or C1 -C24 -alkanoyloxy.
6. A trisazo compound as claimed in claim 1, wherein Y is mono-C1 -C24 -alkylamino, monobenzylamino, monophenylethylamino or monophenylamino and X is bis-C1 -C24 -alkylamino, N-C1 -C12 -alkyl-N-benzylamino, N-C1 -C12 -alkyl-N-phenylethylamino, N-C1 -C12 -alkyl-N-phenylamino, C1 -C24 -alkoxy, benzyloxy or phenylethoxy, where in each case the benzene rings are unsubstituted or substituted by C1 -C12 -alkyl, cyclohexyl, 4-C1 -C12 -alkylcyclohexyl, C1 -C24 -alkoxy, phenoxy or C1 -C24 -alkanoyloxy.
7. A trisazo compound as claimed in claim 1, wherein X and Y independently of one another are each C1 -C24 -alkoxy, benzyloxy or phenylethoxy.
8. A trisazo compound as claimed in claim 1, of the formula ##STR29## where Z and R7 have the given meanings and X1 is C1 -C24 -alkoxy, benzyloxy or phenylethoxy.
Description

Liquid crystal materials which contain pleochroic dyes are used in displays. The principles of the use of dyes in liquid crystal materials are known and are described by, for example, H. Kelker and R. Hatz, Handbook of Liquid Crystals, (1980) 611 et seq, R. J. Cox, Mol. Cryst. Liq. Cryst. Vol. 55 (1979), 51 et seq., and L. Pauls and G. Schwarz, Elektronik 14 (1982), 66 et seq. Further references relating to the use of dyes in liquid crystal materials are cited elsewhere in the stated publications.

Dyes for liquid crystal mixtures must meet a number of requirements (see, for example, B. J. Constant et al., J. Phys. D: Appl. Phys. 11 (1978), 479 et seq., F. Jones and T. J. Reeve, Mol. Cryst. Liq. Cryst. 60 (1980) 99 et seq. and European Pat. Nos. 43,904, 55,838 and 65,869. They must not ionize in an electric field, must have a very high molar extinction coefficient ε and good solubility in the liquid crystal matrix used, must be chemically and, in particular, photochemically stable, and as far as possible must have a degree of order S greater than 0.75 in the particular nematic phase in order to achieve good contrast of the guest-host display.

Dyes which meet all these requirements belong predominantly to the anthraquinone class (see, for example, EP-A-56 492, EP-A-91 225, DE-A-30 28 593, EP-A-54 217 or DE-A-29 01 177).

As a rule, azo dyes known before now have the disadvantage that their light stability and/or their solubility do not meet the high requirements (see, for example, G. W. Gray, Chimia 34 (1980) 47 et seq.).

Symmetrical dichroic trisazo dyes having a high degree of order are known (see, for example, DE-A-31 25 183 or EP-A-54 837).

However, there continues to be a need to improve the degree of order, the solubility and the lightfastness of the dyes, in particular in the low-viscosity and increasingly nonpolar liquid crystal mixtures used today, e.g. ZLI 2452, ZLI 2585, ZLI 2806 or ZLI 2903 from Merck.

It is an object of the present invention to synthesize yellow and red trisazo dyes which possess good solubility and light stability coupled with a high degree of order in the commercial liquid crystal mixtures and which, together with a blue dye, permit the production of a black liquid crystal mixture.

We have found that this object is achieved by the novel trisazo compounds of the general formula I ##STR3## where Z is ##STR4## X and Y independently of one another are each C1 -C24 -alkoxy, benzyloxy, phenylethoxy, mono-C1 -C24 -alkylamino, benzylamino, monophenylethylamino, monophenylamino, bis-C1 -C24 -alkylamino, N-C1 -C12 -alkyl-N-benzylamino, N-C1 -C12 -alkyl-N-phenylethylamino or N-C1 -C12 -alkyl-N-phenylamino, where the benzene rings are unsubstituted or substituted by C1 -C12 -alkyl, cyclohexyl, 4-C1 -C12 -alkylcyclohexyl, C1 -C24 -alkoxy, phenoxy or C1 -C24 -alkanoyloxy, R1, R2, R3, R4, R5 and R6 independently of one another are each hydrogen, methyl, methoxy or chlorine and R7 is hydrogen or methyl, and the ring A or B may furthermore carry a fused benzene ring.

In contrast to the trisazo dyes described in DE-A-31 25 183 or EP-A-54 837, the dyes according to the invention have an asymmetric structure. Surprisingly, we have found that the solubility and also the degree of order in commercial liquid crystals are substantially improved compared with the symmetrical dyes. Furthermore, the dyes possess excellent light stability in solution in liquid crystal mixtures.

Examples of preferred radicals X and Y are butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, dodecyloxy, benzyloxy, 4-(C1 -C12 -alkyl)-benzyloxy, 4-cyclohexylbenzyloxy, 4-(4'-C1 -C12 -alkylcyclohexyl)-benzyloxy, 4-(C1 -C12 -alkoxy)-benzyloxy, 4-(C1 -C24 -alkanoyl)-benzyloxy, butylamino, pentylamino, hexylamino, heptylamino, octylamino, nonylamino, dodecylamino, methylheptylamino, methyloctylamino, methylnonylamino, methyldodecylamino, dioctylamino, didodecylamino, benzylamino, phenylethylamino, 4-(C1 -C12 -alkyl)-benzylamino, 4-cyclohexylbenzylamino, 4-(4'-C1 -C12 -alkylcyclohexyl)-benzylamino, N-methyl-N-[4-(C1 -C12 -alkyl)-benzyl]-amino, N-methyl-N-(4-cyclohexylbenzyl)-amino, N-methyl-N-[4'-C1 -C12 -alkylcyclohexyl)-benzyl]-amino, phenylamino, 4-(C1 -C12 -alkyl)-phenylamino, N-methyl-N-phenylamino and N-methyl-N-[4-(C1 -C12 -alkyl)-phenyl]-amino.

The compounds of the formula I can be prepared by diazotizing a compound of the formula ##STR5## and reacting the product with a coupling component of the formula ##STR6## to give a compound of the formula II ##STR7## where R is hydroxyl or substituted amino an the other symbols having the meanings given above.

Where R is OH, the compounds of the formula II can be converted to the substituted hydroxy compounds by a conventional method.

The nitro compounds of the formula II can, for example, be reduced with sodium sulfide to give the corresponding amino compounds, which are then diazotized again and reacted with a coupling component of the formula ##STR8## to give a compound of the formula I. The conversion of the compounds in which R is OH to the novel compounds containing substituted hydroxyl is in turn carried out by a conventional method.

The dyes can be purified by chromatography over silica gel using, for example, a toluene/ethyl acetate mixture or methylene chloride as the mobile phase. The dyes are then recrystallized, for example from toluene. The purity is preferably checked by thin layer chromatography, HPLC or elemental analysis.

Of particular importance are compounds of the formula Ia ##STR9## where Z and R7 have the stated meanings and X1 is substituted hydroxyl.

Z is preferably quinolylene or naphthylene which is substituted by monosubstituted amino or substituted hydroxyl.

A typical method of preparing the dyes of the formula I is described in Example 1 below. Parts and percentages are by weight, unless stated otherwise.

EXAMPLE 1

150 parts of a 23% strength sodium nitrite solution are first added to a mixture of 124 parts of 4-amino-4'-nitroazobenzene and 1000 parts of water at 5 C., followed by 50 parts of concentrated hydrochloric acid. The mixture is then stirred for 5 hours at 5 C., after which 5 parts of active carbon are added and the mixture is filtered. The filtrate is added to a solution of 54 parts of m-cresol, 20 parts of sodium hydroxide solution and 500 parts of water while cooling with ice, and the pH of the solution is kept at 7 by adding dilute sodium hydroxide solution. The mixture is stirred for a further hour at room temperature, after which the dye formed is filtered off under suction, washed with water and dried. 170 parts (94% of theory) of the bisazo dye of the formula ##STR10## are obtained.

Melting point: 272 C.

A mixture of 54.2 parts of this bisazo dye, 29 parts of n-octyl bromide, 20.7 parts of potassium carbonate and 250 parts of dimethylformamide is stirred for 3 hours at 100 C., and the resulting precipitate is filtered off at room temperature, washed with a little dimethylformamide and then with water and dried. 41 parts (58% of theory) of the alkylated dye of the formula ##STR11## are obtained.

Melting point: 120 C.

35.6 parts of the alkylated bisazo dye in a mixture of 400 parts of water, 250 parts of toluene, 31.6 parts of sodium sulfide and 11 parts of ammonium chloride are heated at the boil for 5 hours. Thereafter, the toluene is distilled off from the mixture, 200 parts of methanol are added and the precipitate is filtered off under suction, washed with methanol and then with water and dried. 23 parts (69% of theory) of the amino compound of the formula ##STR12## are obtained.

Melting point: 182 C.

5.6 parts of the amino compound are dissolved in 60 parts of dimethylformamide, and 3.8 parts of a 23% strength sodium nitrite solution are first added, followed by 3.1 parts of concentrated hydrochloric acid, the additions being made while cooling with ice. The mixture is then stirred for a further 5 hours at 5 C., and a solution of 2.1 parts of ethyl α-naphthylamine in 60 parts of tetrahydrofuran is added to the diazonium salt solution. The resulting precipitate is filtered off under suction, washed with tetrahydrofuran and then introduced into a mixture of 100 parts of methanol and 100 parts of concentrated sodium acetate solution. The mixture is stirred for a further hour at room temperature, and the precipitate which separates out is filtered off under suction and washed with water. 5 parts (64% of theory) of the crude dye of the formula ##STR13## are obtained.

The dye is purified by chromatography over silica gel (silica gel 60, 0.063-0.0200 mm, from Merck) using methylene chloride as the mobile phase, followed by recrystallization from toluene.

Melting point: 167 C.

The dyes listed below can be prepared in a similar manner.

__________________________________________________________________________ ##STR14##     Example          R1                 R2__________________________________________________________________________     1    C8 H17        C2 H5     2    C8 H17        C8 H17     3    C2 H5         C8 H17     4    C7 H15        C12 H25     5    C7 H15                                   ##STR15##     6    C7 H15                                   ##STR16##__________________________________________________________________________Example Dye__________________________________________________________________________  ##STR17##8  ##STR18##9  ##STR19##__________________________________________________________________________ ##STR20##    Example         R1                     R2__________________________________________________________________________    10   C12 H25           NHC2 H5    11   C12 H25           NHC12 H25    12   C8 H17            NHC12 H25    13   C12 H25           OC12 H25    14   C12 H25                                      ##STR21##    15   C12 H25           OC2 H5    16          ##STR22##                                      ##STR23##    17   C12 H25           N(CH3)2__________________________________________________________________________ ##STR24##           Example                R1__________________________________________________________________________           18   C8 H17           19   C12 H25           20                 ##STR25##__________________________________________________________________________

Table 1 which follows summarizes, for Exmaples 1 to 20, the degree of order S measured at room temperature in ZLI 2452 from Merck, the solubility L determined in ZLI 2452, likewise at room temperature (for Examples 1-9 only), the melting point and the absorption maximum in methylene chloride.

The degree of order S was determined in accordance with the known equation S=(CR-1)/(CR+2), in commercial measuring cells with a homogeneous orientation (polyimide). The dichroic ratio CR was determined by measuring the extinctions E" (measurement with light polarized parallel to the preferred direction of the nematic phase) and E (measurement with light polarized at right angles to the preferred direction of the nematic phase) and using the relation CR=E"/E, the dye concentration being chosen so that E" was from 1 to 2. The measurements were carried out in an Acta CIII spectrophotometer from Beckmann.

FIG. 1 shows the extinction E" and E for the compound of Example 1 in ZLI 2452.

The solubility was determined as described below.

50 mg of the particular dye was stirred in 1 ml of the liquid crystal material for 1 week at room temperature, the saturated solution was removed from the residue by centrifuging, and the solubility was determined by comparison of the extinctions.

The light stability of the dyes in the particular liquid crystal material was determined by rapid exposure of the solution in the measuring cell in a Suntest apparatus (Hanau) at 25 C. The dyes exhibited very good photostability, particularly when a UV protective coating was used.

              TABLE 1______________________________________   Degree ofEx-     order S   Solubility L M.p. λmax.ample   (at RT)   (at RT)      C.                               (CH2 Cl2)______________________________________1       0.84      2.1%         167  532 nm2       0.84      0.8%         154  534 nm3       0.81      0.4%         170  534 nm4       0.83      1.2%         136  533 nm5       0.81      0.9%         193  528 nm6       0.78      2.9%         141  528 nm7       0.81      1.0%         138  553 nm8       0.83      1.2%         158  442 nm9       0.81      1.0%         187  537 nm10      0.82                   134  532 nm11      0.83                   158  530 nm12      0.82                   135  533 nm13      0.81                   161  443 nm14      0.82                   164  438 nm15      0.80                   163  440 nm16      0.80                   138  438 nm17      0.80                   156  483 nm18      0.83                   170  533 nm19      0.83                   162  535 nm20      0.81                   124  532 nm______________________________________
Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3941560 *Dec 7, 1973Mar 2, 1976American Aniline Products, Inc.Trisazo polyester materials
US4231746 *Aug 22, 1979Nov 4, 1980Basf AktiengesellschaftDyeing of cellulose-containing textile material and novel dyes for use therein
US4308161 *Aug 4, 1980Dec 29, 1981General Electric CompanyNovel yellow azo dyes and dichroic liquid crystal compositions made therewith
US4308162 *Dec 8, 1980Dec 29, 1981General Electric CompanyNovel yellow azo dyes and dichroic liquid crystal compositions made therewith
US4308163 *Aug 4, 1980Dec 29, 1981General Electric CompanyNovel yellow azo dyes and dichroic liquid crystal composition made therewith
US4308164 *Aug 4, 1980Dec 29, 1981General Electric CompanyNovel yellow azo dyes and dichroic liquid crystal composition made therewith
US4359398 *Dec 22, 1980Nov 16, 1982General Electric CompanyLiquid crystal compositions with novel tris-azo dichroic dyes
US4401369 *Oct 19, 1981Aug 30, 1983Electronic Display Systems, Inc.Nematic host, cholesteric component and tetrakisazo dye
US4600527 *Feb 10, 1983Jul 15, 1986Mitsubishi Chemical IndustriesAzo dyes, mult&color, photochromic
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4952678 *Oct 29, 1987Aug 28, 1990Basf AktiengesellschaftExcellent photostability; solubility; used in liquid crystalline media and dying synthetic polymers or fibers
US5162545 *Oct 12, 1990Nov 10, 1992Basf AktiengesellschaftMalonic acid dyes and polycondensation products thereof
US5389285 *Dec 11, 1989Feb 14, 1995Hercules IncorporatedLiquid crystal coupled dichroic dyes
US5453217 *Dec 17, 1993Sep 26, 1995Mitsubishi Chemical CorporationLiquid crystal composition and liquid crystal display device
US5876627 *Nov 27, 1996Mar 2, 1999Mitsubishi Chemical CorporationDichroic dye liquid crystal composition containing the dye, and liquid-crystal element
Classifications
U.S. Classification534/577, 534/764, 534/809, 534/887, 534/DIG.2, 252/299.1, 534/573, 534/831
International ClassificationC09B35/35, C09B31/16, C09K19/60
Cooperative ClassificationY10S534/02, C09B35/35, C09K19/601
European ClassificationC09K19/60A, C09B35/35
Legal Events
DateCodeEventDescription
Apr 9, 1996FPExpired due to failure to pay maintenance fee
Effective date: 19960131
Jan 28, 1996LAPSLapse for failure to pay maintenance fees
Sep 5, 1995REMIMaintenance fee reminder mailed
Jul 1, 1991FPAYFee payment
Year of fee payment: 4
Oct 9, 1987ASAssignment
Owner name: BASF AKTIENGESELLSCHAFT, 6700 LUDWIGHAFEN, RHEINLA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:ETZBACH, KARL-HEINZ;REEL/FRAME:004769/0842
Effective date: 19860730
Owner name: BASF AKTIENGESELLSCHAFT,GERMANY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:ETZBACH, KARL-HEINZ;REEL/FRAME:004769/0842